Patent GB-107886-A (GB)
IPC: B66C3/08
Abstract: 107,886. Allaire, P. Oct. 2, 1916. Grab-buckets.-In a grab in which the opening and closing of the buckets is effected by a heisting-chain passing around pulleys, the upper pulleys are mounted in a block having a limited vertical :notion in the grab frame, this motion serving to apply and to release gripping-levers which are pivoted to the block and are linked to the frame in such a way that the chain cannot pass upwards but can pass freely downwards when the grips are in action. A second chain connected to the sliding block passes over a locking-device to a balance weight. The grab is shown in side elevation in Fig. 1, the chain grips are shown in Fig. 4, and the mechanism for arresting and keeping taut the opening-chain is shown in Fig. 6. The bucket sections 2 are pivoted at their outer corners 3 to the grab frame 1 and are connected at their inner corners by links or crossed levers 31 to an axle on which three pulleys 13a are mounted. The upper part of the grab frame 1 is formed as a vertical guide for a block 4 which carries pulleys 5, 5a and 6, and is capable of a limited vertical movement in the guide. The hoisting- chain 12 passes down from the jib-head through an opening in the block 4 and is received under the pulleys 13<a> and over the pulleys 5, 5a, its end being attached at 12<a> to the block 4. Chain grips 7 pivotally mounted on pins 8 on the block 4 have rearwardly-extending arms resting on stops 32 and are connected by pins 10 to slotted links 9 suspended on the frame 1. The block 4 is attached t) the opening-chain 20, Fig. 6, which passes over a pulley 21 on the jib-head and is wound on a drum 16, the flanges of which are toothed and may be locked by a slide 23 controlled by a rope 26. A balance weight 19 is supported by a rope 17 also wound on the drum 16. When the open grab is resting on the material, it is closed and lifted by hauling in the hoisting-chain 12, the block 4 being in its lowest position and the grips 7 released. To discharge the grab, the opening- chain 20 is held by the slide 23, and the hoisting- chain is paid out so that the grab frame falls relatively to the block and the grips are placed in position to hold the chain. The grips are arranged, however, to allow the chain to pass downwards and the grab is thus discharged. When the weight of the grab is again taken by the hoisting-chain 12, it is held by the grips 7 and the grab may be transported and lowered in the open position, the grips being released when the grab rests on the material to be lifted. When it is desired to discharge by means of a suspended ring 30, one of the grips 7 carries a hook-shaped arm 27, and a tearward extension 28 is slotted to engage a pin 29 on the frame 1. When the closed grab is being raised, the hook 27 occupies a vertical position so that it takes over the ring 30 to suspend the grab. If the chain 12 is then slackened, the frame 1 falls relatively to the block 4 and applies the grips 7, which, however, allow the chain to pass downwards as before. When the grab has discharged and is open, the chain 12 is hauled in and is held by the grips 7 so that the open grab may be lifted off the ring 30, the hook 27 being then in an inclined position.